Air cleaner for ventilated dynamo-electric machines



June 26, 1962 J. E. RAMSEY 3,041,117

AIR CLEANER FOR VENTILATED DYNAMO-ELECTRIC MACHINES Filed NOV. 29, 1960 INVENTOR JAMES E. RAMSEY BY f f ATTO NEY United States atent 3,641,117 AIR CLEANER FOR VENTILATED DYNAMO- ELECTRIC MACHINES James E. Ramsey, 111 Aiken Road, New Castle, Pa. Filed Nov. 29, 1960, Ser. No. 72,332 4 Claims. (Cl. 310-56) This invention relates to an improved arrangement and apparatus for cleaning the air supplied to the interior workings of a dynamo-electric machine, and more particularly to an improved arrangement for incorporating the air cleaning mechanism in the centrifugal blowers normally utilized to supply a flow of ventilating air longitudinally through the casings of such machines. Heretofore, it has been common practice to house within an end cap of a dynamo-electric machine, such as a motor, an impeller keyed to the machine shaft for the two-fold purpose of creating an air stream for ventilation and for centrifugally cleaning the air before the same enters the machine housing. However, since the cleaning action is by centrifugal force which is coincident with the building up of the forces to create the pressure differential required for moving the air, it is difiicult to separate much of the dust in the air from the air stream entering the machine casing, and I have found that the prior assemblies are deficient in this regard. The problem is one of more effectively sealing the outer ring-like zone of maximum air pressure and maximum dust velocity and concentration from the space within the machine casing so that the air which is therein compressed and the already separated dust particles which are swirling around within this zone will not be again intermixed and drawn into the machine housing.

Accordingly, it is the primary object of the invention to provide, in a ventilating means for dynamo-electric machine, an improved yet simple and practical arrangement for sealing the annular space adjacent the outer periphery of the normally employed ventiiating and cleaning impeller from access to the windings and other parts Within the machine casing. In this manner 1 may employ an impeller of maximum diameter to build up an effective pressure head for ventilation and to insure maximum dust separation yet without encountering the problem of having the substantial air velocities resulting from the higher head pick up the once separated dust particles and draw the same into the machine.

The above object is accomplished in accordance with the principles of my invention by employing a self-lubricating ring-like seal between the space within the machine housing and the space within the end cap or other enclosure for the impeller contiguous to the periphery of the impeller so that no air can enter the casing from the annular Zone housing the outer peripheral portion of the impeller. A small annular space with a discharge outlet is provided radially outward of the impeller for the discharge of grit and dust particles but this space is sufliciently restricted, however, so as not to lose much of the pressure head developed by the impeller. The compressed air is allowed to enter into the machine casing through apertures formed in the impeller well inward radially of the seal.

The above and other objects and advantages of the invention will become more readily apparent upon consideration of the following specification and the accompanying drawing wherein there is disclosed a preferred embodiment of the invention.

In the drawing:

FIGURE 1 is a side elevation, partly in section, of an electric motor having an air cleaning and ventilating impeller incorporated therein in accordance with the principles of my invention; and

FIGURE 2 is an expanded view, in isometric projecice tion, of the parts of FIGURE 1 which are pertinent to the invention.

The machine illustrated has a tubular casing 10 to which is fitted and secured by suitable means, not shown, end caps 11 and 12 each having an outwardly directed boss 13. In accordance with usual practice, bosses 13 retain suitable bearings for journaling the machine shaft 14 on which is secured the rotor 15. Reference numeral 16 denotes the stator of the machine.

An end portion of shaft 14 within one of the end caps-- 12, for examplernay be reduced in diameter and shouldered to receive the hub of a disc-like impeller 17 which, for small machines, is preferably a precision die casting. The impeller 17 is provided on its outer face with a plurality of circumferentially spaced but radially extending vanes 18 which serve to entrap air between the outer face of the impeller and the adjacent wall of the end cap 12 and to force this air with its entrapped grit and dust radially outward under centrifugal force. It should be noted that the end cap 12 has a plurality of air inlet ports 19 adjacent the boss 13 and that these inlet ports are immediately radially inward of the inner ends of the vanes 18.

The peripheral portion of the inner face of the impeller 17 is flanged or lipped as shown at 29 in FIGURE 1, and in practice the face of this lip is accurately die formed or machined to be precisely normal to the axis of the central bore through the hub of the impeller, and this bore is likewise accurately formed or machined to fit tightly on the shaft 14 and with the aid of the aforementioned shoulder to be absolutely normal to the axis of the shaft. The impeller 17 is also provided with a plurality of apertures 21 which, as shown in FIGURE 2, are positioned circumferentially intermediate the vanes 18 and radially intermediate the ends of these vanes.

Clamped between the adjacent end of the casing 10 and the mounting flange of the end cap 12 is the outer peripheral portion of a ring-like seal 22 which in actual practice is made of a tough self-lubricating plastic such a Teflon or nylon. As shown in FIGURE 1, the ring 22 extends radially inward sufficient to overlie the whole of the face of the lip 20 of the impeller 17. Cemented or otherwise suitably secured to the inner face of the ring 22 radially inward of the inner periphery of the casing Iii is a baffle ring 23 having an enlarged central aperture located radially inward of the apertures 21 of the impeller 17 but yet being of sufficiently large diameter to provide for the unrestricted fiow of air axially over the adjacent portion of the machine shaft 14. To complete the assembly of my invention I provide, on the adjacent axial end of the rotor 15 an impeller ring 24 having axial extending blades 25 and, as shown, this ring is made as large in diameter as possible in relation to the diameter of the rotor 15 so that a maximum centrifugal effect for assisting the circulation of the ventilating air may be attained. There is also provided a dust discharge opening in the lowermost portion of the side wall of the cap 12, this opening being protected by a shield 26.

From the above description, it should be observed that the impeller 17 is of maximum practical diameter so that the peripheral velocity and resultant centrifugal force acting on the grit and dust particles contained in the entering air will be of maximum value. When the machine is operating, therefore, such grit and dust particles contained in the entering air will be violently impinged against the side wall of the cap 12 and will be swirled around thereon until they reach the opening in the bottom portion of the side wall where they will be discharged. Such opening may be of substantial circumferential extent to facilitate self-cleaning action of the space within the end cap. However, the annular space intermediate the periphery of the impeller 17 and the side wall of cap 12 is rather restricted, as shown, so that a substantial pressure head of air will be built up in the annular zone of the outer peripheral portion of the impeller. As this pressure builds up, more and more air will move axially inward through the apertures 21 in the impeller 17 and then through the large aperture in the baffle 23 into the region of the vanes 25 of the impeller 24. The centrifugal action imparted by these vanes will assist in moving the air through the ports mentioned and thus further facilitate the circulation of air axially through the electric machine, the air being discharged therefrom through the ports 19 in the end cap 11.

It should be observed particularly that the face of lip 20 of the impeller 17 has a light, sliding, yet accurate fit against the plane side surface of the sealing ring 22 so that the entry of dust and air into the casing it) directly from the annular space about the impeller 17 is effectively restrained. Further, since the sealing plane is normal to the axis of rotation of the impeller, centrifugal force assists in preventing the entry of air and dust in a radial inward direction between the ring 22 and the lip 20. The tight seal between the radially outward portion of the ring 22 and the mounting flange of the end cap 12 of course prevents any axial flow of air and dust radially outward of the impeller.

Having thus described my invention what I claim is:

1. In a dynamo-electric machine having a tubular casing, a rotor, and an end cap fitted over an end of said casing and mounting a bearing for journaling the rotor shaft; the improvement of means to supply cleaned cooling air to said casing comprising a sealing ring clamped between said casing end and said end cap and extending radially inward toward the axis of said shaft, said inwardly extending portion of said ring having a plane surface normal to said axis and exposed to the space within said cap, a disc-like impeller lying within said cap and rigidly mounted on said shaft and having a planar end face adjacent its outer periphery lying in a plane normal to said axis and adapted to have a sliding and sealing fit with said exposed face of said sealing ring, said impeller having a plurality of radially disposed vanes on its side opposite said planar surface, air inlet openings in the end wall of said cap adjacent the center thereof, apertures in said disc-like im peller positioned circumferentially between said vanes and radially intermediate the ends of said vanes, and a dust discharge opening in the lowermost portion of the side wall of the cap.

2. Apparatus according to claim 1 further including an annular disc-like baffle afiixed to the inner side face of said sealing ring, the central opening through said bafiie being of substantially larger diameter than the diameter of said shaft.

3. Apparatus according to claim 2 further including an impeller on the axial end of said rotor adjacent said baflie, said impeller having an outer diameter approximating the outer diameter of the rotor and having a multiplicity of circumferentially spaced vanes extending axially toward said bafiie, said last mentioned vanes being operative by centrifugal effect to aid in drawing air inwardly through the central opening in said baffie.

4. Apparatus according to claim 1 further characterized in that said sealing ring is formed of a self-lubricating plastic material, and the said end face of said impeller being accurately formed to lie in a plane parallel with the sealing face of said sealing ring and normal to the axis of rotation of said shaft.

References Cited in the file of this patent UNITED STATES PATENTS 923,673 Lord June 1, 1909 1,963,401 Clason June 19, 1934 FOREIGN PATENTS 671,285 Germany Feb. 3, 1939 

